brightness doesn't work

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http://askubuntu.com – I used Ubuntu 11.10 on Acer Aspire 4750 with Intel HD Graphics. When I made it up looks like Linux Mint 12, the graphics card was detected as Intel Sandy Bridge x86/MM2. But I still got problem with the brightness. It didn't work, as I had to try some tricks like editing the GRUB, but it still didn't work. Please help me (HowTos)